Quantum cascade laser based absorption spectroscopy for direct monitoring of atmospheric N2O isotopes

Sheng Zhou; Ningwu Liu; Lei Zhang; Tianbo He; Jingsong Li

doi:10.1016/j.saa.2018.07.028

Quantum cascade laser based absorption spectroscopy for direct monitoring of atmospheric N₂O isotopes

Spectrochim Acta A Mol Biomol Spectrosc. 2018 Dec 5:205:79-84. doi: 10.1016/j.saa.2018.07.028. Epub 2018 Jul 10.

Authors

Sheng Zhou¹, Ningwu Liu², Lei Zhang², Tianbo He², Jingsong Li³

Affiliations

¹ Laser Spectroscopy and Sensing Laboratory, Anhui University, 230601 Hefei, China; Key Laboratory of Opto-Electronic Information Acquisition and Manipulation of Ministry of Education, Anhui University, 230601 Hefei, China. Electronic address: optzsh@ahu.edu.cn.
² Laser Spectroscopy and Sensing Laboratory, Anhui University, 230601 Hefei, China; Key Laboratory of Opto-Electronic Information Acquisition and Manipulation of Ministry of Education, Anhui University, 230601 Hefei, China.
³ Laser Spectroscopy and Sensing Laboratory, Anhui University, 230601 Hefei, China; Key Laboratory of Opto-Electronic Information Acquisition and Manipulation of Ministry of Education, Anhui University, 230601 Hefei, China. Electronic address: jingsong_li@ahu.edu.cn.

PMID: 30015032
DOI: 10.1016/j.saa.2018.07.028

Abstract

A compact high-resolution spectroscopic sensor using a thermoelectrically (TE) cooled continuous-wave (CW) room temperature (RT) quantum cascade laser (QCL) operating at 4.6 μm, is employed for simultaneous detection of three main isotopic species (¹⁴N¹⁵N¹⁶O, ¹⁵N¹⁴N¹⁶O and ¹⁴N¹⁴N¹⁶O). To enable a high-precision analysis of N₂O isotopic species at ambient mixing ratios, a liquid nitrogen-free preconcentration unit is built to trap and load atmospheric N₂O. The absorption spectra of ¹⁴N¹⁵N¹⁶O, ¹⁵N¹⁴N¹⁶O, and ¹⁴N¹⁴N¹⁶O between 2188.6 cm^-1 and 2189 cm^-1 are measured, and the respective ratios of the rare to the abundant isotopologues abundances are demonstrated. Moreover, spectroscopic parameters of pressure-broadening coefficient for selected absorption lines have been determined, and a good agreement is obtained by comparing with HITRAN database.

Keywords: Isotope analysis; Laser spectroscopy; Nitrous oxide; QCL.